1. Field of the Invention
This invention relates to a semiconductor light emitting device.
2. Background Art
The semiconductor light emitting device is expanding its applications as a source for infrared red˜yellow˜green˜to blue light and white light, and is required to have high light extraction efficiency and high reliability.
For example, high light extraction efficiency is realized by roughening the light extraction surface of the light emitting device with a large number of concave-convex structures. As total internal reflection of light emitted from inside the light emitting device at the interface between the device surface and the device outside is reduced by the surface roughening, the light extraction efficiency to the device outside can be improved.
JP-A 2006-108635 (Kokai) discloses a semiconductor light emitting device with nanometer-sized concave-convex structures at its surface. This nanometer-sized concave-convex structure includes a nanometer-sized convex structure having a mesa part with graded refractive index, a cylinder with diffraction effect, and a corn with graded refractive index, thereby improving the light extraction efficiency.
However, the formation process of the concave-convex structures at the surface likely induces processing damage. In the case where current spreads laterally in the light emitting device to get light emission from a wide device area, the current may also spread into the damaged region, resulting in deterioration of the brightness.
Band discontinuity between InGaAlP and GaAs is disclosed in M. O. Watanabe et al., Appl. Phys. Lett. 50 (1987) 906 (hereinafter referred to as Non-Patent Document 1). Band discontinuity between GaAlAs and GaAs is described in J. Batey et al., J. Appl. Phys. 59 (1986) 200 (hereinafter referred to as Non-Patent Document 2).